1. Technical Field
The present disclosure relates to an optical system. More particularly, the present disclosure relates to a compact optical system applicable to electronic products.
2. Description of Related Art
In recent years, as the popularity of mobile products with camera functionalities, the demand for miniaturized photographing systems is increasing. The sensor of a conventional photographing system is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact photographing systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact photographing systems featuring better image quality.
A conventional compact photographing system applied in a portable electronic product typically utilizes a three-element lens structure, such as the one disclosed in the U.S. Pat. No. 8,094,231. Due to the popularity of mobile products with high-end specifications, such as smart phones and PDAs (Personal Digital Assistants), the requirements for high resolution and image quality of modern compact optical lens systems increases significantly. However, the conventional three-element lens structure cannot satisfy these requirements of the compact photographing systems. Although the five-element lens structure has a longer total track of length, such as the one disclosed in the U.S. Pat. No. 8,000,030, is not favorable for being applied to compact electronic products.
Another conventional compact photographing system provides a fixed-focus lens system which is a fixed lens system with a fixed focal length. For example, the one disclosed in the U.S. Pat. No. 8,169,528 is a four-element lens structure. It has limited capabilities in focusing an object at a close distance and infinity resulting in producing poor image quality. Therefore, as there is a trend towards compact photographing systems and higher megapixels, having an accurate focusing capability both at a close distance and infinity has become more and more important. Although the digital image processing technique of the extended depth of field (EDOF) can compensate for the deficiency of the fixed-focus lens system, the image quality will be compromised and the consumed power will be more.
Therefore, a photographing system applied in a mobile electronic product for exhibiting a small amount of movement in focusing objects from far to near while maintaining a compact size and low power is needed in the art.